James mccraoken



UNTTED sTATEs PATENT oEEioE.

JAMES MCCRACKEN, OF BLOOMFIELD, NEW JERSEY.

FURNACE.

Specification of Letters Patent No. 19,942, dated April 13, 1858.

ATo all whom t may concern:

Be it known that I, JAMES MGCRACKEN, of the town of Bloomfield, in the county of Essex and State of New Jersey, have invented a new and useful Improvement in Furnaces for the More Perfect Management of Combustion; and I do hereby declare that the following is a full, clear, and exact description, reference being had to the accompanying drawings, making part of this specification, in Which- Figure l is a perspective view, partly in section, of my improved furnace as applied to a steam boiler; Fig. 2, a front elevation; and Fig. 3, a longitudinal vertical section.

The same letters indicate like parts in all the figures.

My invention relates to the construction of a furnace, whether for heating steam boilers or other purposes, with the View to the more perfect combustion of the fuel while at the same time the grate bars of such furnace are rendered more durable. And my said invention consists in the employment of hollow grate bars of sufficient capacity to admit of the passage through them of all the air required for the blast or draft of the furnace when such grate bars are combined with a closed ash pit below the grate bars by means of a suitable passage or passages so that the blast or draft of air for the supply of'combustion in the re chambers shall pass through the said grate bars to the closed ash pit, and thence up, between the grate bars. to supply the air required for the combustion of the fuel on the grate.

My said invention also consists in the .use of tubular bearers to support the grate bars when the said tubular bearers are arranged to receive cold air to be heated in passing through them, and, when heated, to discharge it in suitable passages which deliver it at or near the upper edge of the fire bridge wall, when this is combined with a plate placed over the fire and interposed between the fire and the body to be heated, leaving a suiiicient space bet-Ween the said plate and the top ofthe bridge wall for the escape of the gaseous products of the combustion, the object of the said combination being the better to consume the inflammable gases evolved from the lire than could be effected by any other known combination. As the said interposed plate is not in direct contact with the boiler or other body to be heated itis soon carried to a much higher temperature than a boiler or other body, and being so highly heated the inflammable gases coming in contact with it before passing over the bridge wall they are maintained at a temperature so that when pass-- ing over the bridge wall they meet with a supply of heated air coming from the tubular bearers and are then readily and more effectually inflamed than if they were permitted to come in contact with the bottom of the boiler, &c.

In the accompanying drawing A represents a series of hollow grate bars on which the fuel .in the furnace is placed, and the said hars extend from the front of the furnace to a chamber or passage g ust in front. of the bridge wall D,the said passage or chamber g being a continuation of the ash pit G under the grate bars. The front end of the grate bars is controlled by a hinged door h which controls the admission of air to the said grate bars, although other means of control may, be employed. Then the said door is thrown up air enters the grate bars freely, passes through them, and in passing prevents the bars from being overheated, while the air in passing through becomes highly heated and escapes at the rear end into the chamber g, G, or ash pit, which is closed so as. to prevent access of air eX- cept through the said grate bars. The air .thus heated passes up from the ash pit between the grate bars to support the combustion of the fuel on the bars.

There is a door z' to the ash pit, but this is only to be used for cleaning out the ash pit, and, if desired, for the admission of air when kindling the fire; but after this the said door is to be closed that all the air required to support combustion in the fire chamber may pass through the hollow grate bars. If a blast be applied it must be con-- nected with the open front ends of the grate bars in any suitable manner.

The grate bars are supported on tubular bearers B, B, one end of which communicates with and receives cold air from the surrounding atmosphere, which becomes heated in passing through them, and which when heated is discharged at the other end into an open space in the side wall of the furnace, the said space being made to communicate with an open space f in the bridge wall. The air, in this way, is still further heated, and when heated is discharged near the upper edge of the bridge wall D into the flue so as to intercept the gaseous products of combustion as they pass over the bridge wall into the main flue, and are there inflamed.

J ust over the fire is placed a. shield plate C, interposed between the lire and the bottom of the boiler or other body to be heated by the furnace, and the rear edge of the said shield plate extends a little beyond the bridge wall and a short distance above the upper edge of it, leaving a narrow flue space for the passage of the gaseous products of combustion. It is well known that much fuel is wasted in all furnaces by the escape of unconsumed inflammable gases evolved from the fuel. These gases if supplied with a sufficient quantity of atmospheric air will be inflamed and give out intense heat, but. they will not be inflamed even when supplied with atmospheric air unless they are at a high temperature. If the shield plate were not so placed the furnace would be covered by the bottom of a boiler or other vessel containing substances to be 1heated, the heat imparted to the bottom of such vessel would be carried 'off and absorbed by the water orother substance to be heated, and this rapid absorption of the heat would of necessity keep down the temperature of the upper part of the fire chamber, and hence the gases in coming in contact with such boiler or other vessel would give out their heat, and would be thereby so much reduced in temperature as not to be inflammable when meeting a supply of air at or beyond the bridge wall. This is the very diii'iculty heretofore experienced in furnaces, which diiiiculty is remedied by the introduction of the shield plate above described, for the said shield plate will become highly heated and` will maintain the inflammable gases at a high temperature until they meet the current of heated air by which they are readily iniialned, and will give out their heat in passing through the flue. The said shield plate at the same time protects that part of the boiler which extends over the furnace from being too highly heated.

I do not claim as of my invention the employment of hollow grate bars for the passage of air through them, as such have before been known and used; nor do I claim supplying air to the gaseous products of combustion for the combustion of the inflammable gases evolved from the fuel; nor do I claim the heating of the air to be supplied to the inflammable gases; nor finally do I claim the use of a shield plate to protect the bottom of a boiler and prevent it from being overheated, as all these have long been known; but

That I do claim as my invention and desire to secure by Letters Patent is- 1. The employment of hollow grate bars in combination with a closed ash pit in the manner substantially as herein described, so that the air which passes through the said grate bars shall be discharged into the ash pit, and thence pass up between the said grate bars to supply the blast or draftV to the fire on the grate bars, as set forth.

2. I also claim the use of tubular bearers for supplying heated air to the infiammable gases at or near the fire bridge, substantially as described, in connection with a shield plate substantially as described, and interposed between the fire and boiler or other body to be heated, constructed and arranged as specified, to maintain the infiammable gases at a high temperature until after they are supplied with heated air for their ignition, as described.

JAMES MCCRACKEN. Witnesses:

J. W. BAILEY, WM. H. BISHOP. 

